The MRI apparatus is an image diagnostic apparatus which magnetically excites nuclear spin of an object set in a static magnetic field with an RF signal having the Larmor frequency and reconstructs an image based on MR (magnetic resonance) signals generated due to the excitation.
Into cables of RF coils used in an MRI apparatus, unbalanced currents received from a transmission RF coil and surrounding electric circuits flow. These unbalanced currents can cause a breakage of a circuit element in an RF transceiver system or a degradation in an image quality. Since plural RF coils are usually used in an MRI apparatus, the unbalanced currents are generated in each of the cables connected to the RF coils.
Accordingly, a balun circuit is conventionally connected with cables of RF coils in order to inhibit an influence of the unbalanced currents. The balun circuit has a cylindrical structure. Then, composite cables, in which signal lines and a power source line are bundled, pass through the inside of the balun circuit. In recent years, an MRI apparatus has plural balun circuits in an RF transceiver system and bundled composite cables pass a common balun circuit multiple times.